Needle stick injuries among medical personnel such as health care workers are of growing concern because of disease transmission, particularly the deadly virus io known as HIV-1 (AIDS) and Hepatitis B. The AIDS virus for which there is no known cure is estimated to infect more than twenty million people worldwide and is spreading rapidly. Although in 1985 medical publications stated that no health care workers had become infected with the AIDS virus, it is now known that there is a significant risk to health care workers. A report in the New England Journal of Medicine, Aug. 14, 1988, indicates that the risk of acquiring HIV-1 infection is 0.35-0.74% per needle stick injury. The reported incidence of needle stick injuries to medical staff has been reported at 25.3 per 100 beds annually. In one New York hospital, at least 7% of house doctors have sustained needle stick injuries while caring for AIDS patients.
Transmission rates of Hepatitis B after needle stick exposure are much higher than that occurring with the HIV virus and may be 6-30%. The Center for Disease Control has estimated 200-300 health care workers die annually in the U.S.A. from occupationally acquired Hepatitis B.
With presently used syringes with projecting needles, potentially dangerous needle stick injuries are commonplace and most often occur between the time the medication is injected into the patient and the time the syringe is disposed of. Most injuries occur while recapping the needle or when disposing of it into a disposal container. However, maintenance personnel who handle disposed materials are also subject to needle stick injuries.
At present, there is no reason to believe that the AIDS epidemic will come to a quick end. Canada's frequency rate at the present time is 100.2 cases per 1,000,000. The United States is a frightening 377.1 cases per 1,000,000. In Canada, according to current data projections, the incidence of AIDS rate at least doubles every eighteen months.
A number of patents disclose syringes or the like having needle protecting features. In spite of this there are no syringes which allow withdrawal and safe entrapment of needles currently on the market. This suggests difficulties with manufacture of prior patent designs. The syringe which is the subject of this patent application is manufacturable and commercially viable. In addition, after proper medical use the syringe cannot be reused and any toxic substances or infections contained within the barrel are not accessible without physical breakage of the syringe. U.S. Pat. No. 4,592,744, Jagger et al., Jun. 3, 1986, illustrates a disposable medical needle apparatus with a self-sheathing safety needle assembly. The self-sheathing safety needle has a case with a small closed end and a large open end. A needle assembly is located within the case with the needle projecting through the small closed end. A hub is connected to the needle assembly inside the case. The connector on the hub cooperates with a receiver on the small end to hold the needle assembly in the case. A flange on the hub cooperates with an inward projection in the case based from the small end to prevent movement of the needle out of the case when the needle is withdrawn from the opening in the small end. The nozzle of a syringe pushed into the hub withdraws the needle when the syringe is withdrawn. A rubber stopper on a vacuum tube withdraws the needle after the rubber stopper turns the flange to release the connector from the receiver.
U.S. Pat. No. 4,804,370, granted Feb. 14, 1989, Haber et al., discloses a disposable disease control syringe which reduces the frequency of accidental needle strikes to health care workers and prevents health-threatening reuse of the needle cannula by drug abusers. The syringe includes a cylinder having an open proximal end, a substantially closed distal end, and a retractable needle projecting through the distal end. A piston assembly having a detachable stem and a needle capturing receptacle moves axially and distally through the syringe cylinder to expulse fluid medication and to selectively engage the needle at the most distal aspect of the cylinder. The piston assembly is then withdrawn proximally through the cylinder, whereby to relocate the needle from the distal end to the proximal cylinder end. The needle capturing receptacle is locked at the proximal end of the syringe cylinder with the needle cannula retracted within and completely shielded by the cylinder. The stem is then detached from the piston assembly and discarded, thereby creating a disposal cartridge with the needle cannula rendered permanently irretrievable therewithin. Alternatively, the piston assembly can be driven distally through the cylinder for correspondingly moving the needle into contact with a puncture resistant shield located at the distal end of the cylinder, whereby the needle is axially collapsed and destroyed within the cylinder.
U.S. Pat. No. 4,542,749, Caselgrandi et al., and U.S. Pat. No. 3,306,290, Weltman, disclose syringes with protected needle designs.
U.S. Pat. No. 4,631,057, Mitchell, discloses a syringe which has on the body of the syringe a needle guard which can be moved from a position which shields the needle, to a retracted position which exposes the needle. U.S. Pat. No. 4,425,120, Sampson, granted Jan. 10, 1984, also discloses a shielded hypodermic syringe with a needle guard mounted on the barrel which may be extended or retracted to protect or expose the needle. U.S. Pat. No. 4,573,976, Sampson et al., also discloses a shielded needle syringe comprising a needle guard which can be retracted or extended relative to the body of the syringe, means being provided for releasably retaining the guard in the retracted position. U.S. Pat. No. 3,884,230, Wulff, granted May 20, 1975, discloses a flexible needle guard and device for a hypodermic syringe. This design appears to be directed mainly to avoiding breakage of the needle when the syringe is being used.
U.S. Pat. No. 4,258,713, Wardlaw, discloses an automatic disposable hypodermic syringe which has means for driving the hypodermic needle from a retracted position within the housing of the syringe to an injecting position whereby a portion of the needle protrudes from the housing. This device does not disclose a feature whereby the needle can be protected or retracted after use. U.S. Pat. No. 4,085,737 discloses a blood sampling syringe which includes an apparatus for protecting the open end of the needle of the syringe. The device is intended for minimizing risk of contamination of the needle tip after a blood sample has been taken. U.S. Pat. No. 4,260,543, Blum, granted May 12, 1981, discloses a hypodermic needle protection means which is designed so that the needle can be slidably moved to the interior of the needle support means upon application of pressure.
U.S. Pat. No. 4,266,544, Wardlaw, granted May 12, 1981, discloses an improved disposable syringe wherein retracting means movably mounted on the housing of the syringe is adapted to pull the needle from its projecting position to a safe position whereby the needle is covered by a portion of the syringe. U.S. Pat. No. 4,139,009, Alvarez, discloses a hypodermic needle assembly with a retractable needle cover, the needle cover comprising a plurality of elastically resilient arms extending between a hub portion and a slide member, the arms acting as a restoring force for urging the slide member back over the needle forward portion when the syringe is withdrawn from contact with the skin of a patient.
U.S. Pat. No. 4,774,964 discloses a device which is designed to withdraw blood from a patient. It is not a syringe per se. It is not used for injecting fluids into a patient. However, the device has the capacity to withdraw the needle into the barrel housing.